| Flowering time is one of the most important traits in hybird corn. Molecular genetic markers not only help in defining the genetics of the trait but also may facilitate map-based cloning of its major quantitative trait loci (QTLs). About 280 primers were utilized to identify RAPD markers closely linked to a QTL on chromosome 8L in a cross between N28 and N28E20, a line derived from 20 backcrosses of N28 with Gaspe Flint as donor for early flowering. Four RAPDs showed close linkage with the chromosome XL maturity QTL.; Bulked segregant analysis (BSA) was utilized to verify whether the chromosomal regions controling the number of days to pollen shed (DPS) in crosses previously evaluated at the University of Minnesota were also involved in the control of DPS in Mt42xNC254, A679xNC254, and A86-9xR225. Of the seven putative QTLs for DPS detected by BSA, five QTLs were among those previously identified. The importance of the QTL for DPS on the chromosome 8L region near UMC89 was confirmed in Mt42xNC254 and A679xNC254. This region has been shown to affect DPS in more than ten different genetic backgrounds.; The association between the concentration of abscisic acid in the leaf (L-ABA) and DPS was tested. The results obtained from the field evaluation of the early and late F3 families derived from Mt42xNC254, A679xNC254, and A86-9xR225 indicated a positive, but weak, association between L-ABA and DPS in A679xNC254 and in A86-9xR225. The QTL analysis carried out on 151 (A662xB73) F3 families evaluated for GABA in two samplings at two locations revealed the presence of seven QTLs influencing L-ABA. Among these QTLs, only two (on chr. 5 and chr. 8) influenced L-ABA in both locations. The QTL on chr. 5 peaked 16 cM from UMC54, a marker which was also associated with a QTL for DPS. At this region, a delay in flowering was associated with an increase in L-ABA. These results, indicate that ABA may represent one of the factors playing an inhibitory role in the switch from the vegetative to the reproductive phase in maize. |
